1. Field of the Invention
The present invention generally relates to an improvement in ring laser gyroscope signal processing systems, and more particularly to a signal processing system for adjusting the relative phase angle of the rate readout signals to establish a quadrature relationship between them.
2. Description of the Prior Art
As will be appreciated by those skilled in the art, a ring laser gyroscope (RLG) of the type contemplated by this invention, comprises a pair of laser beams rotating in opposite directions about a closed loop path. Interference between the beams creates an interference pattern of alternately bright and dark bands. As the closed loop path rotates, the interference pattern of light and dark bands moves relatively to a photodetector optically coupled to the path. The detector output is a sinusoidal signal whose frequency is a function of rate of rotation of the closed loop path. As will also be appreciated by those skilled in the art, two signals are advantageously generated in response to the interference pattern that are phase displaced 90 degrees one from the other. This pair of quadrature signals allows the RLG signal processing system to determine direction of rotation as well as rate of rotation.
Ideally the quadrature signals are precisely 90 degrees out of phase with respect to one another. However, tolerances in the RLG components and in its assembly procedure can and do cause quadrature errors in the output signal in a completely assembled RLG, so that the phase difference between signals is greater or less than 90 degrees. To the extent there is a quadrature error there is a potential degradation in the maximum rate capability of the RLG.